Entity Framework - Enum Support

Advertisements

Previous Page
Next Page  

In Entity Framework, this feature will allow you to define a property on a domain class that is an enum type and map it to a database column of an integer type. Entity Framework will then convert the database value to and from the relevant enum as it queries and saves data.

  • Enumerated types have all sorts of benefits when working with properties that have a fixed number of responses.

  • The security and reliability of an application both increase when you use enumerations.

  • Enumeration makes it much harder for the user to make mistakes, and issues such as injection attacks are nonexistent.

  • In Entity Framework, an enumeration can have the following underlying types −

    • Byte
    • Int16
    • Int32
    • Int64
    • SByte

  • The default underlying type of the enumeration elements is int.

  • By default, the first enumerator has the value 0, and the value of each successive enumerator is increased by 1.

Let’s take a look at the following example in which we will be creating an entity in designer and then will add some properties.

Step 1 − Create new project from File → New → Project menu option.

Step 2 − In the left pane, select the Console Application.

Creating Entity

Step 3 − Enter EFEnumDemo as the name of the project and click OK.

Step 4 − Right-click on the project name in Solution Explorer and select Add → New Item menu option.

Step 5 − Select ADO.NET Entity Data Model in the Templates pane.

Data Model Template

Step 6 − Enter EFEnumModel.edmx for the file name, and then click Add.

Step 7 − On the Entity Data Model Wizard page, select Empty EF designer Model.

Model Wizard Page

Step 8 − Click Finish

Step 9 − Then right click on designer window and select Add → Entity.

Designer Window Entity

The New Entity dialog box appears as shown in the following image.

New Entity Dialog

Step 10 − Enter Department as an Entity name and DeptID as a property name, leave the Property type as Int32 and click OK.

Step 11 − Right click the entity and select Add New → Scalar Property.

Scalar Property

Step 12 − Rename the new property to DeptName.

Step 13 − Change the type of the new property to Int32 (by default, the new property is of String type).

Step 14 − To change the type, open the Properties window and change the Type property to Int32.

Type

Step 15 − In the Entity Framework Designer, right click the Name property, select Convert to enum.

Entity Framework Designer

Step 16 − In the Add Enum Type dialog box, enter DepartmentNames for the Enum Type Name, change the Underlying Type to Int32, and then add the following members to the type: Physics, Chemistry, Computer, and Economics.

Add Enum

Step 17 − Click Ok.

If you switch to the Model Browser window, you will see that the type was also added to the Enum Types node.

Model Browser Window

Let’s generate database from model by following all the steps mentioned in Model First approach chapter.

Step 1 − Right click Entity Designer surface and select Generate Database from Model.

The Choose Your Data Connection Dialog Box of the Generate Database Wizard is displayed.

Step 2 − Click the New Connection button.

Connection Button

Step 3 − Enter the server name and EnumDemo for the database and click OK.

Step 4 − A dialog asking if you want to create a new database will pop up, click Yes.

Step 5 − Click Next and the Create Database Wizard generates data definition language (DDL) for creating a database. Now click Finish.

Step 6 − Right-click on T-SQL Editor and select Execute.

TSql Editor

Step 7 − To view the generated schema, right click on the database name in SQL Server Object Explorer and select Refresh.

You will see the Departments table in the database.

Departments Table

Let’s take a look at the following example in which some new Department objects to the context are added and saved. And then retrieve the Computer department.

class Program {

   static void Main(string[] args) {

      using (var context = new EFEnumModelContainer()) {

         context.Departments.Add(new Department { DeptName = DepartmentNames.Physics});
         context.Departments.Add(new Department { DeptName = DepartmentNames.Computer});
         context.Departments.Add(new Department { DeptName = DepartmentNames.Chemistry});
         context.Departments.Add(new Department { DeptName = DepartmentNames.Economics});

         context.SaveChanges();

         var department = (
            from d in context.Departments
            where d.DeptName == DepartmentNames.Computer
            select d
         ).FirstOrDefault();

         Console.WriteLine(
            "Department ID: {0}, Department Name: {1}", 
               department.DeptID, department.DeptName
         );

         Console.ReadKey();
      }
   }
}

When the above code is executed, you will receive the following output −

Department ID: 2, Department Name: Computer

We recommend that you execute the above example in a step-by-step manner for better understanding.

Advertisements